Electron tube



F. HERRIGER ELECTRON TUBE April 15, 1941.

Filed Sept. 10, 1938 IHH , ,4 N NNNNNNN Patented Apr. 15, 1941 ELECTRONTUBE Felix Herriger, Berlin, Germany, assignor to C. LorenzAktiengesellschaft, Berlin-Tempelhof (Germany) Lorenzweg, a companyApplication September 10, 1938, Serial No. 229,245 In Germany September13, 1937 4 Claims.

In the manufacture of electron tubes intended for very high frequencies,especially for a wave range below 3 meters, it is found that theselfcapacities of the electrodes and the inductances of the leads to theelectrodes assume values so high that practically it is not possible foroscillations to be amplified, the feed-back coupling effected by theinter-electrode capacities causing undesired oscillations to arisethrough self-excitation.

In order to avoid such self-excitation it has been proposed to arrangeneutralization condensers within the vacuum vessel. By this means,however, an inductive drop of potential along the cathode leads isoccasioned, whereby the symmetry effected by the neutralizationcondensers is undone.

In order to overcome this drawback the invention proposes to arrange twoelectrode systems adapted for push-pull operation and two neutralizationsystems in one discharge vessel common to them. A special advantageobtained in this way is that the leads to the cathodes carry merelydirect current.

In accordance with another feature of the invention the neutralizationsystems are preferably in the nature of cold electrode systems.

The invention will be understood from the following description,reference being had to the accompanying drawing in which Fig. 1 showsthe circuit arrangement of the electrode systems, Fig. 2 represents asomewhat diagrammatic longitudinal section through an example ofelectron tubes as provided by the invention, Fig. 3, drawn to a largerscale than Fig. 2, shows a section on line 3-3 of Fig. 2, Fig. 4 is adiagrammatic detail view of a cathode arrangement adapted for tubes ofthe novel type, Fig. 5 is a fragmentary plan, viewed in the direction ofthe arrow, of the cathode arrangement represented in Figs. 2 and 3. Fig.6 is a longi tudinal sectional view of the electrode structure of thetubes shown in Fig. 2, taken at right angles to Fig. 2.

In Fig. 1 all of the component capacities and component inductances,contained in tubes as provided by the invention, are represented. I, IIdenote the component capacities of the heated electrode systems, whileIII, IV indicate the component capacities of the cold electrode systemsthat serve as neutralization systems. Each of these parts I to IVcomprises the grid-anode capacity Cga, the grid-cathode capacity 090 andthe anode-cathode capacity Cac. The inductances of the grid leads aredesignated Lg. The

inductances of the anode leads are denoted by La while those of thecathode leads are desi nated L0. The electrode systems of the tube arecontrolled over a coil A whereas the output power is taken over a coil Bof a single anode circuit. The single cathode-lead is earthed at E. Thearrangement here shown is perfectly neutralized in itself, so that noself-excitation of oscillations shall be possible. Also, no highfrequency current will flow in the cathode lead earthed at E.

In a vacuum vessel I two cathodes 2,, 3, two grids 4, 5 and two anodes6, l are arranged in the manner illustrated in Figs. 2, 3 and 6. Thecathodes are strip-shaped or fiat and are parallel to the anodes 6, I.As shown in Figs. 3 and 5, cathode 2 has an emissive layer It. Fig. 5also shows the cathode 3 to be provided with an emissive layer Hi. Thelayers 18, It are located on opposite sides of the axis of vessel I.

This electrode system involves the capacity distribution represented inFig. 1, that is to say, cathode 2, grid 4 and the appertaining parts ofthe anodes 6, 1 correspond to the parts I, III, Fig. 1. One side of thiscomponent system, namely the side in which the emissive layer It iseffective, forms the heated electrode system while the other or oppositeside thereof forms the cold system which serves for neutralization. Thearrangement here disclosed by way of example has the special advantagethat the control grid and the appertaining grid portions acting asneutralization condenser are directly interconnected, the connectingconductors thus having practically no self-induction. This effect isincreased by the grids being formed as coils the turns of which aresubstantially vertical to the axis of the cathodes 2, 3.

Accordingly cathode 3, grid 5 and the appertaining parts of the anodes6, l are arranged to act as the parts II, IV, Fig. 1.

The grid voltages are supplied from coil A, Fig. 1, over leads 8, Whilethe anode currents are taken through leads 9. In order to effect acontinuous transition of the surge impedance from the anodes B, l to theleads 9, the points at which these leads are joined to the anodes arefitted with a sheet metal covering III.

In the manufacture of the arrangement here described the leads 8, 9 arefixed in a ceramic ring H in the direction of radii. Then the saidelectrode systems are arranged and two glass hoods 12 are secured toring H. In the vessel I thus formed the electrode systems are held inplace by means of insulating discs [3, It, for

instance. In order that win the case of high power tubes a directlyheated cathode can be employed, a second wire-shaped cold cathode I5 isadded to a heated cathode l5, th two being arranged to cross in themiddle, as represented in Fig. 4. Cathode I6 is to prevent the emissioncurrent from being controlled by the neutralization system. Similarly,the screening between the heated system and neutralization system may beeffected by a suitable piece of sheet metal. Also, the two grid-cathodesystems may be located beside each other, the cathodes then having to beinterconnected by short conductors. In the case of high power tubes theanodes may be hollow bodies and two hollow leading-in members may beattached to the anodes in order to provide for cooling these bycirculatory water. If such Water cooling is employed, the entireelectrode system may be arranged in a closed ceramic vessel.

The neutralization systems instead of being in the nature of coldelectrode systems as here before described, may be composed ofcondensers and coils.

A screening I! of sheet metal may be arranged to surround the leads 8 inthe manner appearing from Fig 3, such screening being of cathodepotential.

What is claimed is:

1. An electron tube comprising a first cathode and a second cathode, afirst anode facing a first surface of both said cathodes, a second anodefacing a second surface of both said cathodes, a first grid coiledaround one of said cathodes, a second grid coiled around the other ofsaid cathodes, and means to prevent electron current from flowingbetween said first surface of said first cathode and said second anodeand between said second surface of said second cathode and said firstanode.

2. An electron tube according to claim 1 wherein said first and secondcathodes are emissive on their second and first surfaces respectivelyand are non-emissive on their other surfaces, and wherein said cathodesare adapted by their dimensions to prevent the electric fields of saidfirst and second anodes from influencing the electron fiow from saidfirst and second surfaces respectively.

3. An electron tube as defined in claim 1, wherein the cathodes arestrip-shaped, and are indirectly heated, only one side thereof beingprovided with emissive layer.

4. An electron tube according to claim 1, having non-heated screeningmeans adapted to protect the cathodes from being influenced by thefields of the neutralization systems.

FELIX HERRIGER.

